An agricultural harvester, also referred to as a combine or combine harvester because it typically combines multiple harvesting functions, typically includes a header for removing a crop from a field and a so-called threshing tool for performing a threshing operation on the crop in order to separate the grain from the non-grain material such as straw and chaff. The non-grain material may also be referred to as the residue. This residue, i.e. the chaff and straw is typically left on the field. In general, the chaff is spread in the field over the width of the combine. With respect to the straw, typically two options exist.
In a first operating mode, referred to as “swath mode”, the straw is outputted onto the field in a so-called swath, ready for a baler to pick it up.
In a second operating mode, referred to as “chopping mode”, the straw is chopped and outputted on the field where it serves as fertilizer for the soil. The straw is therefore chopped fine to obtain an optimal rotting process such that it can be absorbed into the soil thereby setting free minerals for subsequent crops.
In order to obtain an effective fertilization of the soil it is important that the chopped straw, in general the crop residue, is sufficiently small and that the chopped straw is evenly, or uniformly distributed over the field. As such, the crop residue should be distributed over a width substantially corresponding to a width of the header of the harvester that cuts the crop. In order to distribute or spread the crop residue, e.g. chopped straw, agricultural harvesters are typically equipped with a spreader tool that is mounted at the back of the harvester. The spreading tool is configured to receive a flow of chopped straw and deflect it to both the right hand sight and the left hand sight of the harvester. It is known that the way the residue or chopped crop is affected by different parameters, e.g. including the elevation of the field, the wind direction and magnitude, the density of the chopped straw, etc.
In order to improve the distribution of the residue or chopped straw, monitoring systems have been suggested. Examples of such monitoring systems include the use of a camera to picture the swath of chopped straw leaving the harvester, or the use of wind vanes and/or wind velocity sensors. In another example, the use of a pair of ultrasonic sensors is suggested, the pair of ultrasonic sensors that are directed to the respective streams of chopped straw towards the left hand side and the right hand side of the harvester.
None of these arrangements however enables to assess the distribution of the chopped straw over the entire width of the header of the harvester. Therefore, there is a need for an improved monitoring system for assessing the distribution of chopped straw as outputted onto a field.